#!/usr/bin/perl -w

$S="[01]";

print "\nEnter string:  ";
while (<STDIN>) {
  chomp;
  print "The string matches:  ";
  print "1 " if /^0*10*$/;
  print "2 " if /^$S*1$S*$/;
  print "3 " if /^$S*001$S*$/;
  print "4 " if /^($S$S)*$/;
  print "5 " if /^($S$S$S)*$/;
  print "6 " if /^(01|10)$/;
  print "7 " if /^(0|1|0$S*0|1$S*1)$/;
  print "8 " if /^$/;
  print "6x " if /^01|10$/;               # this is wrong
  print "7x " if /^0|1|0$S*0|1$S*1$/;     # this is wrong
  print "\n";

  print "\nEnter string:  ";
}